1. Field of the Invention
The present invention is directed to a shock wave generator for an installation for non-contacting disintegration of calculi in the body of a life form, and in particular to such a shock wave generator having a coil with spirally arranged turns and a membrane of electrically conductive material lying opposite the coil and terminating a space filled with a fluid, the coil being connectable to a high-voltage supply.
2. Description of the Prior Art
A coil and membrane shock wave generator having a membrane arranged parallel to the coil is disclosed in German OS No. 33 12 014. The shock waves are generated by connection of the coil to a high-voltage supply which contains a capacitor charged to a plurality of kilovolts, for example 20 kV. The energy stored in the capacitor then discharges suddenly into the coil, the result being that the coil builds up a magnetic field with extreme rapidity. At the same time, a current is induced in the membrane which is opposite the current flowing in the coil which consequently generates an opposing magnetic field under whose influence the membrane is suddenly moved away from the coil. The shock wave thus generated in the fluid-filled space, for example in a water-filled space, is focussed in a suitable manner onto the calculi, for example kidney stones, situated in the body of the life form, and effecting the disintegration thereof.
In order to achieve the greatest possible conversion of the electrical energy output by the high-voltage supply into shock energy, it is required in the known shock wave generator to attach the membrane optimally close to the coil. Due to the difference in potential necessarily existing between the coil and the membrane, however, this is only possible within limits since a minimum spacing must be observed in order to avoid arcing between the membrane and the coil. Arcing deteriorates the effect of the shock wave generator and leads to damage to the membrane, thereby decreasing its useful life. In the known shock wave generator, therefore, the distance between the membrane and the coil must be selected in the interest of an adequate useful life of the membrane such that an unsatisfactory efficiency is achieved in the conversion of electrical energy into shock energy.